<?php
define('DB_HOST','localhost');
 define('DB_USER','user_name'); 
 define('DB_PASS','your_password');
define('DB_NAME','review_app' );
//新建连接

$conn = new mysqli(DB_HOST, DB_USER, DB_PASS, DB_NAME);
//检查连接

if ($conn->connect_error) {
    die("连接失败" . $conn->connect_error);
 }
 echo "连接成功!";